A reversible and stable doping technique to invert the carrier polarity of MoTe₂

Abstract

Two-dimensional (2D) materials can be implemented in several functional devices for future optoelectronics and electronics applications. Remarkably, recent research on p–n diodes by stacking 2D materials in heterostructures or homostructures (out of plane) has been carried out extensively with novel designs that are impossible with conventional bulk semiconductor materials. However, the insight of a lateral p–n diode through a single nanoflake based on 2D material needs attention to facilitate the miniaturization of device architectures with efficient performance. Here, we have established a physical carrier-type inversion technique to invert the polarity of MoTe2-based field-effect transistors (FETs) with deep ultraviolet (DUV) doping in (oxygen) O2 and (nitrogen) N2 gas environments. A p-type MoTe2 nanoflake transformed its polarity to n-type when irradiated under DUV illumination in an N2 gaseous atmosphere, and it returned to its original state once irradiated in an O2 gaseous environment. Further, Kelvin probe force microscopy (KPFM) measurements were employed to support our findings, where the value of the work function changed from ∼4.8 and ∼4.5 eV when p-type MoTe2 inverted to the n-type, respectively. Also, using this approach, an in-plane homogeneous p–n junction was formed and achieved a diode rectifying ratio (If/Ir) up to ∼3.8 × 104. This effective approach for carrier-type inversion may play an important role in the advancement of functional devices.

Atomic Layer MoTe2 Field-Effect Transistors and Monolithic Logic Circuits Configured by Scanning Laser Annealing

“…As shown in Figure d, the methods for realizing n-type MoTe 2 FETs reported to date include intrinsic n-type MoTe 2 , chemical doping, surface charge transfer doping (SCTD), and contact engineering . Our n-type MoTe 2 FETs exhibit higher mobility than counterparts reported in previous studies. ,,− ,,,− In addition, MoTe 2 FETs with fewer numbers of layers (<12 layers) exhibit declined mobility due to enhanced Coulomb impurity scattering …”

“…Possible solutions include a number of unconventional atomic doping and surface modification techniques that are being explored, such as molecular doping, − surface charge transfer or electron doping, − electrical activation, , focused laser irradiation, − and deep ultraviolet (DUV) irradiation. , These methods mainly involve surface dopants or H 2 O in the atmosphere, MgO film evaporated by electron-beam evaporation, O 2 /H 2 O via electrothermal annealing induced by an electric field, or doping in the channel due to generation of vacancy defects and excess O atoms induced by laser irradiation . Another route is electrostatic doping achieved through gating, where the presumably dominant transport carrier type in the 2D channel is often regulated and dominated by a Schottky barrier (SB). , However, the state-of-the-art method of tailoring the SB height has been limited to employing contact metals with different work functions.…”

Bipolar Junction Transistor Exhibiting Excellent Output Characteristics with a Prompt Response against the Selective Protein

“…A DUV light was exposed over the MoTe 2 flake in a nitrogen gas environment under a pressure of 5 × 10 4 Pa to enhance its electron density. This light‐assisted, N 2 + DUV‐induced doping enhanced the density of electrons in the MoTe 2 flake [ 18,20 ] (Figure S2a,b, Supporting Information). Using the dry transfer technique, a few layers of thin (≈4 nm) p‐GeSe flakes were transferred over the pre‐transferred, N 2 + DUV‐treated n‐MoTe 2 flake.…”

“…[12,16,17] Here, we introduce an n-p-n BJT device composed of heavily doped molybdenum ditelluride (n-MoTe 2 ) and germanium selenide (p-GeSe) sheets stacked on each other by vdW interactions. The bottom MoTe 2 sheet acts as an emitter and is exposed to deep-UV (DUV) in a nitrogen environment to increase the electron density, [18,19] collector current (I c ), and gain of the BJT device. An undoped MoTe 2 sheet is used as a collector owing to its low electron concentration.…”

Effect of an optimal oxide layer on the efficiency of graphene‐silicon Schottky junction solar cell

“…9 Various efforts have been accomplished to increase the PCE by using several approaches including graphene films with a different number of layers, 10,11 chemical doping to enhance the doping effect in graphene, [12][13][14] and by applying light-trapping layers or anti refection coating to absorb incident light all the way. [15][16][17] The enhancement in PCE and stability of the photovoltaic solar cells are the key factors to determine its potential for industrial applications. Up to now, many reports have been published based on graphene/silicon 18 photovoltaic solar cells but still, the PCE of the photovoltaic (PV) cell is lower than the conventional Si-based solar cell due to recombination of charge carrier caused by low barrier height in case of graphene/silicon Schottky junction.…”